The studies outlined in this proposal extend our current experiments aimed towards understanding the role of testis-specific basic proteins during mammalian spermatogenesis. The primary objective of this sudy is to isolate and chemically characterize the three testis-specific basic proteins from the mouse. Additional limited structural studies on the purified H2S and protein "A" would provide information regarding their primary structure and distinguish them from other somatic histones. Antisera directed specifically against the testis histones H1, H2S and protein "A" have been produced in rabbits and used for their immunocytochemical localization. The data indicates H2S to be specific to germ cells unlike H1 variant and protein "A" which occur both in the somatic and germ cells. However, the distribution of these two proteins in spermatogenic nuclei is quite distinct from the pattern observed in somatic nuclei. Additional studies indicate that the neonatal and embryonic germ cell nuclei may be enriched in protein "A," thereby facilitating immunocytochemical detection of prospermatagonia during embryogenesis. These studies have documented for the first time, a nuclear marker or embryonic germ cells. The experiments proposed here would extend this observation and may provide new insights into the orgin and development of germ cells during mammalian embryogenesis. Additional studies on chromatin organization, testis-specific basic protein mRNA's, product analysis of in vitro synthesized proteins using testis mRNA'a, synthesis of specific CDNA probes may aid in understanding the role of H2S, protein "A" and H1b during mammalian spermatogenesis. It is anticipated that these studies will enable us to gain a better understanding of mammalian spermatogenesis at the molecular level. A better understanding of cellular and molecular processes specific to mammalian spermatogenesis may also aid in developing more rational approaches towards male fertility and infertility problems.